Ultrasonic transducers for use in various applications are discussed in the related art. Ultrasonic transducers are used, for example, in fluid media such as gases and/or liquids to measure a fill level and/or a flow property, for example a mass or volumetric flow, or a velocity of the fluid medium. In particular, ultrasonic transducers of this type are used in the intake tract and/or exhaust gas tract of internal combustion engines. As an alternative or in addition, ultrasonic transducers may also be used, for example, as distance sensors in air or other gases or liquids. Examples of ultrasonic transducers are discussed in DE 203 02 582 U1, EP 0 766 071 A1 or in DE 10 2007 010 500 A1.
Ultrasonic transducers may have at least one electric-acoustic transducer element, for example a piezoelectric transducer element, which is configured to convert electrical signals to ultrasonic signals and vice versa. Ultrasonic transducers are known from the related art which are based on a piezoceramic and which may additionally include at least one impedance matching layer, for example a λ/4 impedance matching layer, the electric-acoustic transducer element and the at least one optional impedance matching layer forming a transducer core. This transducer core may be introduced into a housing, for example a housing sleeve. The housing usually has at least one opening which faces the fluid medium and which may also be referred to as the radiation opening. To seal the housing interior, in which the transducer core is usually accommodated, against the fluid medium, it is believed to be understood, in principle, to apply a sealing film to this opening.
For example, post-published DE 10 2008 055 126.0, DE 10 2008 055 116.3, DE 10 2009 046 149.3, DE 10 2009 046 146.9 and DE 10 2009 046 147.7 discuss ultrasonic transducers of this type, in which a radiation opening is sealed by a sealing film. Since the sealing film itself represents an important interface of the connection between the transducer core and the fluid medium, whose quality is crucial for the radiation characteristic of the ultrasonic transducer, there remains a need for a reliable connection between a sealing film and an ultrasonic transducer housing, in particular for the purpose of measuring ultrasonic air masses in internal combustion engines, but also for other applications.